Using purrr::walk to save the files - invalid 'description' argument

user_17969464 0
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I have problems with saving files using looping. I first wrote a function which works well without loop. However, it always fail with loop. Can anybody tell me the reason?

a<-c(1,2,3)
b<-c(4,5,6)
c<-c(7,8,9)

data<-data.frame(a,b,c)
path<-list('path1/', 'path2/')

test<-function(data,path){
  write.csv(data,file = paste0(path,'result.csv'))
}

purrr::walk(path, test(data=data, path=path))
# Warning in if (file == "") file <- stdout() else if (is.character(file)) { :
#   the condition has length > 1 and only the first element will be used
# Error in file(file, ifelse(append, "a", "w")) : 
#   invalid 'description' argument
purrr r
1 Answers

The warning about condition has length is because you are passing path=path which is length 2, and the file= argument of write.csv expects length 1.

You think that you're using walk to iterate over values, but you need to use a function or ~ quasi-function.

This works:

purrr::walk(path, ~ test(data=data, path=.))

The . can also be .x and is a placeholder for each of the values within the first argument to walk: path. A "standard" function use would be

purrr::walk(path, function(P) test(data=data, path=P))

(which also works).

user_33582720
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